The fouling of industrial water systems due to the presence of macroinvertebrates is a constant problem. Whether an industrial water system is a once-through or a recirculating system, the system will be vulnerable to contamination by macroinvertebrates. The extent and type of macroinvertebrate fouling will depend upon many factors such as the source of the cooling water, the season, the water temperature, the growth rate of the fouling macroinvertebrate and the linear velocity of the water in the system.
For example, mollusks are common macroinvertebrates which can cause macrofouling problems to marine and fresh water cooling systems. Macrofouling by mollusks, like other groups of macrofouling microinvertebrates--barnacles, bryozoans, sponges, hydroids, trunicates and annelids--is initiated by the settlement or attachment of larval and or juvenile stages that are easily entrained by the surface waters of cooling systems. Fouling caused by the settlement, attachment and/or growth of the mollusks in the cooling system and associated service water systems of industrial plants and utilities which utilize large quantities of water is a major problem causing a variety of deleterious effects to the structure, operation and safety of the systems.
The growth of microbiological contaminants in industrial water systems is a similar problem. The formation of slime by microorganisms is a problem in both cooling water systems and pulp and paper mill systems. In those once-through and recirculating cooling systems which employ large quantities of water as a cooling medium, the formation of slime by microorganisms is an extensive and constant problem.
Because of the problems attendant with the presence of macroinvertebrates, slime or microorganism growth the use of controlling biocides is common. Biocides, such as quaternary ammonium salts have proven to dramatically increase system efficacy by creating an uninhabitable environment for the macroinvertebrates or the microorganisms. For example, U.S. Pat. No. 4,857,209 described a method of controlling the fouling potential of macroinvertebrates such as mollusks in aqueous systems which employs a water soluble quaternary ammonium salt. The water streams from cooling towers and other industrial water systems that are treated by such biocides may contain residual amounts of the material upon release into the natural environment. Such release may result in the death of fish or other wildlife.
Concerns with respect to such discharge of waste products into natural waters has grown significantly in recent years. This growing concern is manifested, in part, in the actions of municipal, state and federal authorities who have either already enacted legislation to eliminate the pollution of our natural waters or who are in the process of promulgating such regulations. The regulations and legislations enacted by representative authorities are becoming more and more stringent with the ultimate goal being the prohibition of the addition of any material to natural water which has even an insignificant effect on the life which exists therein.
In response to such legislation, industrial users of large volumes of water have sought out methods of decreasing effluent toxicity. See for example U.S. Pat. No. 3,524,812 which teaches a method of decreasing the biocidal effects of bromonitrostyrene by reaction with a compound selected from a water soluble sulfite compound, hydrogen peroxide and potassium permanganate. U.S. Pat. No. 4,204,954 teaches a method of detoxifing residuals of quaternary ammonium salt biocides in water by neutralizing with anionic monomers such as sodium stearate.
The addition of clays to waters treated with quaternary ammonium salt biocides prior to release into the environment is known. Such materials, particularly bentonite clay, have been shown in laboratory and field tests to be effective at detoxifying quaternary ammonium compounds thereby avoiding wildlife kills. While clays have been shown to be effective treatments for the detoxification of biocides they are troublesome to feed, particularly during moist or rainy weather.
As a partial solution to these feeding problems water based slurries containing clay have been developed. The feeding of an aqueous slurry of clay is relatively problem free, however, such clay slurries are limited to approximately 23% active levels by viscosity and stability limitations. The limited actives level (about 23%) in such slurries results in increased costs for shipping and handling due to the large volume of water present. Prior to the present invention, the use of a "high solids" clay based slurry for quaternary ammonium based biocide detoxification was unknown. By "high solids" content it is meant actives level in an aqueous slurry above 23% and preferably up to about 50% or higher.